Method for powering an apparatus

ABSTRACT

An internal combustion engine is coupled to a supercharger operable to supply varying amounts of air to the engine responsive to the load on the engine. The supercharger has a pair of screw rotors driven by the engine to move air to the engine and a control apparatus for varying the mass and pressure of air supplied to the engine.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/800,870 filed May 25, 2010. Application Ser. No. 12/800,870 is acontinuation of U.S. patent application Ser. No. 11/391,700 filed Mar.28, 2006, now U.S. Pat. No. 7,726,285. Application Ser. No. 11/391,700claims the benefit of the priority of U.S. Patent Application Ser. No.60/666,891 filed Apr. 1, 2005.

FIELD OF THE INVENTION

The technology of the invention relates to internal combustion enginesequipped with superchargers for supplying air to the engines accordingto the speed and load of the engines to increase the performance of theengines.

BACKGROUND OF THE INVENTION

Air displacement devices have been developed and used to increase thesupply of air and fuel to internal combustion engines to boost enginehorsepower. An example of an air displacement device is the “Rootsblower” shown by P. H. Roots in U.S. Pat. No. 30,157 and G. Scheerer inU.S. Pat. No. 2,201,014. This device has a belt-driven shaft that drivestwo close-clearance rotors. The rotating rotors during each rotationsweep out a specific volume of air to an air receiver, such as aninternal combustion engine. The rotational speed of the rotors largelydetermines the unthrottled volume of air discharged by the device. C. N.Hansen and P. C. Cross in U.S. Pat. No. 6,241,498 disclose asupercharger having cooperating rotors drivably connected to an internalcombustion engine for delivering an air/fuel mixture to the combustionchamber of the engine. The rotors have semi-cylindrical pockets andprotrusions that continuously move air through the supercharger. Theunthrottled volume of air discharged by the supercharger depends on theoperating speed of the engine that drives the supercharger. Theunthrottled volume of air discharged by the supercharger operating at aconstant speed varies little. There are no air flow controls to regulateair flowing into and out of the supercharger.

J. E. Whitfield in U.S. Pat. No. 3,151,806 discloses a screw typecompressor having a pair of screw rotors rotatably mounted on a housing.Volume control valves are located on the fluid inlet side of a fixedvalve spacer. Compression control valves located on the fluid outletside of the fixed valve spacer regulate the size and length of the fluiddischarge outlet. Screws connected to the valves are used to adjust thepositions of the valves to provide desired variations in fluid deliveryvolume and internal compression ratio.

F. Soderlund and K. Karlsson in U.S. Pat. No. 4,597,726 disclose a screwcompressor having two rotors rotatably mounted on a housing for mutualmeshing engagement. The pressure ratio and the capacity of thecompressor is regulated with two slides mounted for independent axialmovements. One slide regulates the capacity of the compressor. The otherslide regulates the built-in volume ratio of the compressor.

N. Tsubol in U.S. Pat. No. 4,951,638 discloses a screw type superchargerhaving a pair of female and male screw rotors. Gears mounted on one endof each rotor synchronize rotation of the rotors so that they do notcontact each other. One rotor is connected to an internal combustionengine which provides input power to the supercharger. The superchargerdoes not include intake air flow controls that regulate the volume ofair discharged to an internal combustion engine intake manifold.

J. Oscarsson in U.S. Pat. No. 4,802,457 discloses an internal combustionengine equipped with a supercharger having screw rotors located in acompression chamber. An air capacity regulating device associated withthe air inlet side of the supercharger is operated by the footaccelerator when the engine is only partially loaded.

A. B. Riach in U.S. Pat. No. 5,791,315 discloses a spark ignitioninternal combustion engine coupled to a supercharger having an air inletport control for controlling the intake air into the supercharger. Thecontrol includes an inlet port valve which is open at full engine loadand progressively closes when the engine load is progressively reducedand an air flow throttle valve which is open at full engine load andprogressively closes when the load is progressively reduced.

G. Kirsten in U.S. Pat. No. 6,022,203 discloses a variable displacementscrew-type compressor having a pair of rotors operable to move fluidunder compression from an inlet channel to an outlet channel. Housingsegments associated with the rotors control the internal compressionratio of the compressor. Control cams rotated with a stepper motordisplace the housing segments against the bias of springs.

Four stroke diesel engines do not require blowers or superchargers tosupply compressed air for starting and continuous operation. In a fourstroke diesel engine the first down stroke of the piston draws air intothe cylinder. The air in the cylinder is compressed on the upstroke toabout 1,000 pounds per square inch. Near the top of the stroke of thepiston a jet of fuel oil begins to spray into the cylinder and isauto-ignited by the hot compressed air in the cylinder. The rapidpressure rise of the fuel oil created by the rapid burning of the gasmoves the piston down in the working stroke. The subsequent upstrokedrives the exhaust gases and particulates out of the cylinder through anexhaust valve to an exhaust manifold. The output torque of a four strokediesel engine is controlled by varying the amount of fuel oil injectedand burned in the cylinder. The volume of air in a naturally aspirateddiesel engine cylinder during each air intake stroke varies little withthe speed or torques of the engine but does limit the maximum quantityof fuel that can be injected per cycle.

SUMMARY OF THE INVENTION

The invention constitutes a four stroke diesel engine operably connectedto a load, such as an electric generator, combined with a variableinternal compression ratio supercharger for supplying varying amounts ofair to the diesel engine to match the rate of air flow delivered to thediesel engine with the rate of air flow drawn by the diesel engine suchthat no air pressure rise occurs in the air intake manifold of thediesel engine when additional power output of the diesel engine is notrequired. The supercharger is a positive air displacement mechanismpowered by the diesel engine. The supercharger has intake air flowcontrols that regulate the volume of air discharged by the superchargerto the diesel engine to maintain the speed of the diesel enginesubstantially constant when driving large variable loads than a smallerengine could without the supercharger. Air is moved through thesupercharger with a pair of rotating screw rotors or one female and onemale screw having cooperating helical grooves and protrusions or landsthat create positive air flow to the diesel engine. The volume of airflow discharged by the supercharger is regulated by controlling theeffective air pumping length of the screw rotors. A plurality of gatesassociated with the rotors control the air pumping operation of therotors. Actuators, such as solenoids, connected to the gates function tomove the gates between out and in positions relative to the rotors. Whenall of the gates are in the “in” positions a maximum volume of air ispumped by the supercharger into the diesel engine to facilitate coldstarting of the diesel engine. The volume of air supplied to the dieselengine by the supercharger is changed by selectively moving the gatesbetween their out and in positions. A controller responsive to the speedand load on the engine actuates the solenoids to control the volume ofair supplied to the diesel engine to maintain the diesel speed and loadrequirements of the diesel engine. The variable compression ratiosupercharger produces the lowest parasitic losses to the system byminimizing the pumping work required of the supercharger to meet thecurrent load requirement.

An object of the invention is to improve the power to weight ratio ofdiesel engines to replace gasoline engines for mobile electric powergenerators. Another object of the invention is to combine a superchargerand four stroke diesel engine to improve the engine's portability andreduce its size and weight. A further object of the invention is tocombine a four stroke diesel engine and a positive displacement airsupercharger having the ability to efficiently adjust boost air pressureto the engine over the engine operating range to increase the fuelefficiency of the engine. Yet another object of the invention is toprovide a variable positive displacement air supercharger for a fourstroke diesel engine that can boost air pressure at cold cranking speedsto enhance the starting of the diesel engine, allowing the engine tobenefit from a lower compression ratio once started for after-startrunning efficiency.

DESCRIPTION OF DRAWING

FIG. 1 is a diagram of a four cylinder diesel engine and supercharger ofthe invention connected to an electric generator;

FIG. 1A is a diagram of the engine and supercharger of FIG. 1 for amotor vehicle;

FIG. 2 is a side elevational view of the supercharger;

FIG. 3 is a top plan view of the supercharger;

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 2;

FIG. 5 is a sectional view taken along the line 5-5 of FIG. 2;

FIG. 6 is a sectional view taken along the line 6-6 of FIG. 2;

FIG. 7 is a sectional view taken along the line 7-7 of FIG. 2;

FIG. 8 is a perspective view of a gate of the supercharger shown in FIG.2;

FIG. 9 is a front plan view of the gate of FIG. 8;

FIG. 10 is a side elevational view of the supercharger partly sectionedshowing all the air flow control gates in the in or closed diesel enginestart position;

FIG. 11 is a side elevational partly sectioned view according to FIG. 10showing all of the air flow control gates in the open or out dieselengine naturally aspirated unboosted position;

FIG. 12 is a side elevational view partly sectioned according to FIG. 10showing the first air flow control gate in the in diesel engine lightboost position;

FIG. 13 is a side elevational view partly sectioned according to FIG. 10showing the first and second air flow control gates in the diesel engineintermediate or half boost position;

FIG. 14 is a side elevational view partly sectioned according to FIG. 10showing the first, second and third air now control gates in the dieselengine an increased boost position; and

FIG. 15 is a side elevational view partly sectioned according to FIG. 10showing the first, second, third and fourth air flow control gates inthe diesel engine full boost positions.

DESCRIPTION OF THE INVENTION

The supercharged diesel engine system 10 of the invention, shown in FIG.1, has a conventional four stroke internal combustion piston engine 11that uses the heat of highly compressed air to ignite a spray of fuel,such as hydrocarbon fuel oil introduced into the combustion chambers.This type of internal combustion engine is known as a four stroke dieselengine. Engine 11 includes an air intake manifold 12 for accommodatingan air supply for the combustion chambers of the engine. Fuel injectors13 have solenoids wired to a controller 14 operable to timely supplyhydrocarbon fuel, known as diesel fuel, to the combustion chambers ofengine 11. Controller 14 is wired to a sensor 16 that senses the timingand rotational speed of the output or drive shaft 17 of engine 11. Thesignals from sensor 16 are processed by the electronic components ofcontroller 14 whereby controller 14 generates electric output energythat timely actuates injectors 13 to discharge fuel into the combustionchambers of the engine when the pistons are near the top of theirstrokes.

Drive shaft 17 is connected to an electric generator 18 which supplieselectric power to an electrical load 19. Load 19 is one or more electricpower systems including electric motors, lights, data processingequipment, and heating and air conditioning units. The electric powersystems have varying electric energy requirements which change the loadon electric generator 18. Increased load on generator 18 requires engine11 to increase its power output. Fuel injectors 13 add additional fuelto the combustion chambers of engine 11 to increase the power output ofengine 11. Excess fuel exhausts as smoke and unburned hydrocarbons. Thespeed of engine 11 may slow down as the load on generator 18 increases.The reduction of the speed of generator 18 can be undesirable as it mayalter the electric frequency and voltage output of the generator 18.Generator 18 is typically designed to operate at a constant speed toproduce a constant and reliable electric frequency power output. Dieselengine 11 can be used to operate machines, motor vehicles, ships andother apparatus that require operating power. FIG. 1A illustrates theengine 11 and supercharger 21 of FIG. 1 combined with a motor vehicle18A. For example, diesel engines having capacities of 100 to 5,000 hpare used on industrial and municipal electric generators and oncontinuously operated pipeline oil pumps.

Air is supplied to intake manifold 12 of the engine with a superchargerindicated generally at 21. Supercharger 21 is drivably connected toengine front drive shaft 20 with a power transmission 22, such as a beltand pulley drive. Power transmission 22 can be a gear drive. Theoperating speed of supercharger 21 is directly proportional to therotational speed of drive shaft 20 of engine 11.

Supercharger 21, shown in FIGS. 2, 4, 5 and 6, has a generallyrectangular housing 24 and end walls 26 and 27 attached to opposite endsof housing 24. The top wall 28 of end wall 27 has an air discharge port29 in communication with air intake manifold 12 of engine 11. As shownin FIG. 3, port 29 has a generally rectangular shape with a bottom wallthat extends upwardly and rearwardly. As shown in FIGS. 6 and 7, theinterior of housing 24 has side-by-side cylindrical chambers 31 and 32.A first female rotor 33 mounted on shaft 34 is located in chamber 31.Rotor 33 has a plurality of helical semi-cylindrical grooves 36 havinghelical extents of about 270 degrees in the outer wall of the rotor.Rotor 33 has six circumferentially spaced helical grooves. The numberand helical extent of the grooves can vary. A second male rotor 37mounted on shaft 38 is located in chamber 32. Rotor 37 located generallyparallel to rotor 33 has a number of helical semi-cylindricalprotrusions or lands 39 projected in radial outward directions from theouter wall of rotor 37. The size, shape and helical twists of lands 39are complimentary to the size, shape and helical twists of helicalgrooves 36 in rotor 33. Rotor 37 has four helical lands 39 whichcooperate with six helical grooves 36 in rotor 33. Lands 39 have helicalextents of about 270 degrees along the length of rotor 37. Other landand groove shapes, numbers, sizes and helical extents can beincorporated into cooperating screw rotors 33 and 37. Shaft 34 isrotatably mounted on bearings 35 and 40 retained in end walls 26 and 27.Shaft 38 is rotatably mounted on bearings 45 and 50 retained in endwalls 26 and 27. Bearings 40 and 50 have a slip fit on end wall 26 toallow for thermo expansion of rotors 33 and 34.

As shown in FIGS. 5 and 6, shafts 34 and 38 are drivably connected withgears 41 and 42 which concurrently rotate rotors 33 and 37 in oppositecircular directions. Other types of power transmission devices, such asan endless belt and pulley drives, can be used to drivably connectshafts 34 and 38. An end cover 83 enclosing gears 41 and 42 is attachedto end plate 27.

Returning to FIG. 1, motor 11 rotates shaft 34 thereby turning rotors 33and 37 and moving air through supercharger 21 into manifold 12. Thevolume of the air discharged by supercharger 21 into manifold 12 ischanged or altered to meet the load 19 of electric generator 18.Supercharger 21 operates to substantially match the rate of air flowdelivered to manifold 12 with the rate of air now drawn by the dieselengine.

As shown in FIGS. 2 and 7, housing 24 has an upright U-shaped wall 43and inside shoulders 55 surrounding a chamber 44. A plate 46 connectedto wall 43 covers the top of chamber 44. End plate 26 closes the frontof chamber 44. As shown in FIG. 4, end plate 26 has a plurality of airintake openings 47 open to the air inlet ends of chambers 31 and 32accommodating rotors 33 and 37. Air intake openings 47 surround theportions of end plate 26 that rotatably support shafts 34 and 38. An airinlet cover 49, shown in FIGS. 2, 3 and 6, is attached to the outer sideof end plate 46. Cover 49 has a central tubular extension 51 having apassage 52 to allow air, shown by arrow 53, to flow into supercharger21. Air filters and air pre-cleaners can be associated with extension 51to filter and clean air flowing to the inlets ends of chambers 31 and32.

The flow of air in chambers 31 and 32 along the length of rotors 33 and37 is regulated with a plurality of movable side-by-side gates 54, 55,56, 57 and 58, shown in FIGS. 7 and 10 to 15, located in chamber 44. Thenumber and sizes of the gates can vary according to the air movingcapacity of the supercharger. Gate 58, shown in FIGS. 8 and 9, is a flatplate 59 having flat opposite surfaces 61 and 62 and concave lowersurfaces 63 and 64 concentric with the outer surfaces of rotors 33 and37. Opposite ends 66 and 67 of plate 59 are flat surfaces extendedupwardly to a top plate 68 having outwardly directed stops 69. Fastenersshown as bolts 74 and 76 secure plates 68 to plate 59. A cylindrical rodor core 71 extends upwardly from the center of the top of plate 68. Apair or holes 72 and 73 in plate 68 accommodate bolts 74 and 76 whichsecure plate 68 to plate 59. As shown in FIG. 7, rod 71 extends througha hole in plate 68. The lower end of rod 71 has a head 70 located in arecess 75 in the top of plate 59. Gates 54 to 58 have the same structureas gate 58. Stops 69, shown in FIG. 7, on opposite sides of gates 54 to58 engage shoulders 55 when the gates are in the in or closed positions.Stops 69 prevent the lower surfaces of gates 54 to 58 from contactingrotors 33 and 37. Gates 54 to 58 are selectively moved to out and inpositions relative to rotors 33 and 37 with solenoid actuators 77, 78,79, 80 and 81 wired to controller 14, as shown in FIG. 1. Solenoidactuator 81 mounted on plate 46 includes a rod or core 71 extendedthrough a sleeve bearing 82 mounted on plate 46. The head 70 on thelower end of core 71 is connected to gate 58 with plate 68. Whensolenoid actuator 81 is energized gate 58 is pulled up to an outposition, shown in broken lines in FIGS. 7 and 15, reducing the volumeof air moved by rotors 33 and 34 to manifold 12. Gates 54 to 57 aremoved to out and in positions with solenoid actuators 77 to 80 to varythe volume of air moved by rotors 33 and 37 into manifold 12 accordingto the air flow volume drawn by the diesel engine. Controller 14responsive to the load on engine 11 selectively and jointly actuates thesolenoids 77 to 80. Mechanical cams, lift rollers in push-pull tracks,lever systems and fluid operated cylinders can be used to selectivelyand concurrently move gates 54 to 58 to out and in positions.

As shown in FIG. 10, gates 54 to 58 are located in down or in positions.The lower surfaces of each gate 54 to 58 are positioned adjacent theouter surface of the lands of rotor 37 and the outer surface or rotor33. When gates 54 to 58 are all closed, rotors 33 and 37 move a maximumvolume of air per revolution to manifold 12 of diesel engine 11. Gates54 to 58 are in down positions adjacent rotors 33 and 37 during the coldstarting of diesel engine 11.

As shown in FIG. 11, all of gates 54 to 58 are located in lip or outpositions. The lower surfaces of gates 54 to 58 are spaced above rotors33 and 37 and allow air to flow along chamber 44 whereby only a smallamount of air per revolution is moved by rotors 33 and 37 to airdischarge port 29 in communication with manifold 12 of engine 11. Gates54 to 58 are out when additional boost is not required to meet the powerload on engine 11. The displacement volume of supercharger 21 when gates54 to 58 are all out is related to the engine displacement so that whengates 54 to 58 are out the intake manifold pressure remains essentiallyat atmospheric pressure. This assures that as gates 54 to 57 are movedin the internal air pressure in supercharger 21 closely matches theintake manifold air pressure. This results in the most efficientoperation of engine 11 with no boost or varying levels of boost. Theterm boost is the air pressure in the intake manifold 12 aboveatmospheric pressure.

As shown in FIG. 12, gate 54 is in “in” position and gates 55 to 58 arein “out” positions. When gates 55 to 58 are in “out” positions, airflows in chamber 44, circulates back to intake ends of the rotors andflows to “in” position gate 54 before rotors 33 and 37 begin to move airto air discharge port 29. The amount of air moved by rotors 33 and 37 isincreased thereby increasing intake manifold air pressure aboveatmospheric pressure allowing engine 11 to meet the load efficiently inthis power band.

As shown in FIG. 13, gates 54 and 55 are in “in” positions and gates 56and 58 are in “out” positions. When gates 56 to 58 are in “out”positions, air flows in chamber 44 to “in” position gate 55 beforerotors 33 and 37 begin to move air to air discharge port 29. The amountof air moved by rotors 33 and 37 when gates 54 and 55 are closed allowsengine 11 to efficiently run between this load range.

As shown in FIG. 14, engine 11 runs at the next level of boost whengates 54 to 56 are in “in” positions. Gates 57 and 58 remain open toallow engine 11 to efficiently run in this range of the next level ofboost.

As shown in FIG. 15, engine 11 runs at full boost when gates 54 to 57are in “in” positions and gate 58 is in an “out” position. Gate 58 isonly in the “in” position during the starting of engine 11.

The invention has been shown and described with reference to thepreferred embodiment. Any number of gates can be used to control airflow of the supercharger. The number and size of the gates can vary withthe air moving capacity of the supercharger. Modifications andalterations of the positive displacement air supercharger and air flowcontrols can be made by persons skilled in the art without departingfrom the invention.

1. A method for supplying power with a diesel engine to an apparatuscomprising: operating a diesel engine having at least one combustionchamber for accommodating air and combustible fuel, drivably connectingthe diesel engine to the apparatus whereby the diesel engine powers theapparatus and the apparatus imparts a power demand on the diesel engine,generating a signal of the power demanded of the diesel engine,delivering the signal of the power demanded of the diesel engine to acontroller operable to provide output command signals of the powerdemanded of the diesel engine, supplying air to the combustion chamberof the diesel engine with a supercharger comprising a positive airdisplacement device having at least one movable member operable to varythe effective displacement of the positive air displacement device suchthat it varies the trapped air volume generally at the point that theinternal air compression of the supercharger begins, operating thesupercharger to generate the air supplied to the combustion chamber ofthe diesel engine, varying the air supplied by the supercharger to thecombustion chamber of the diesel engine by operation of the movablemember responsive to the command signals from the controller of thepower demanded of the diesel engine to selectively boost the flow of airdelivered to the combustion chamber of the diesel engine at or above thenaturally aspirated flow of air to the combustion chamber of the dieselengine, and introducing combustion fuel into the combustion chamber ofthe diesel engine responsive to the command signals from the controllercorresponding to the boost of the flow of air delivered to thecombustion chamber of the diesel engine.
 2. The method of claim 1including: providing a motor vehicle apparatus having the diesel engine.3. The method of claim 1 including: drivably connecting the superchargerto the diesel engine to operate the supercharger to generate a supply ofair to the combustion chamber of the diesel engine.
 4. A method forsupplying power with an internal combustion engine to an apparatuscomprising: operating an internal combustion engine having at least onepiston chamber for accommodating air and combustible fuel, drivablyconnecting the internal combustion engine to the apparatus whereby theinternal combustion engine powers the apparatus and the apparatusimparts a power demand on the internal combustion engine, generating asignal of the power demanded of the internal combustion engine,delivering the signal of the power demanded of the internal combustionengine to a controller operable to provide output command signals of thepower demanded of the internal combustion engine, supplying air to thepiston chamber of the internal combustion engine with a superchargercomprising a positive air displacement device having at least onemovable member operable to vary the displacement of the positive airdisplacement device such that it varies the trapped air volume generallyat the point that the internal air compression of the superchargerbegins, operating the supercharger to generate the supply of air to thepiston chamber of the internal combustion engine, varying the airsupplied by the supercharger to the piston chamber of the internalcombustion engine by operation of the movable member responsive to thecommand signals from the controller of the power demanded of theinternal combustion engine to selectively boost the flow of airdelivered to the piston chamber of the internal combustion engine at orabove the naturally aspirated flow of air to the piston chamber of theinternal combustion engine, and introducing combustible fuel to theinternal combustion engine responsive to the command signals from thecontroller corresponding to the boost of the flow of air delivered tothe piston chamber of the internal combustion engine to maintain adesired air to fuel ratio in the piston chamber of the internalcombustion engine.
 5. The method claim 4 including: providing a motorvehicle apparatus having the internal combustion engine.
 6. The methodof claim 4 including: drivably connecting the supercharger to theinternal combustion engine to operate the supercharger to generate asupply of air to the piston chamber of the internal combustion engine.7. A method for supplying power with an internal combustion engine to anapparatus comprising: operating an internal combustion engine having aplurality of piston chambers for accommodating air and combustible fuel,drivably connecting the internal combustion engine to the apparatuswhereby the internal combustion engine powers the apparatus and theapparatus imparts a power demand on the internal combustion engine,generating a signal of the power demanded of the internal combustionengine, delivering the signal of the power demanded of the internalcombustion engine to a controller operable to provide output commandsignals of the power demanded of the internal combustion engine,supplying air to the piston chambers of the internal combustion enginewith a supercharger comprising a positive air displacement device havingat least one movable member to vary the displacement of the positive airdisplacement device such that it varies the trapped air volume generallyat the point that the internal air compression of the superchargerbegins, operating the supercharger to generate the supply of air to thepiston chambers of the internal combustion engine, varying the airsupplied by the supercharger to the piston chambers of the internalcombustion engine by operation of the movable member responsive to thecommand signals from the controller of the power demanded of theinternal combustion engine to selectively boost the flow of airdelivered to the piston chambers of the internal combustion engine at orabove the naturally aspirated flow of air to the piston chambers of theinternal combustion engine, and introducing combustible fuel to theinternal combustion engine responsive to the command signals from thecontroller corresponding to the boost of the flow of air delivered tothe piston chambers of the internal combustion engine to maintain adesired air to fuel ratio in the piston chambers of the internalcombustion engine.
 8. The method claim 7 including: providing a motorvehicle apparatus having the internal combustion engine.
 9. The methodof claim 7 including: drivably connecting the supercharger to theinternal combustion engine to operate the supercharger to generate asupply of air to the piston chambers of the internal combustion engine.10. A method for supplying electric power to an electric load with aninternal combustion engine comprising: operating an internal combustionchamber having an air intake passage and at least one piston chamber foraccommodating air and combustible fuel, supplying electric power to anelectric load with an electric generator, drivably connecting theinternal combustion engine to the electric generator whereby theinternal combustion engine operates the electric generator to supplyelectric power to an electric load and the electric generator imparts aload on the internal combustion engine, sensing the load on the internalcombustion engine and providing a sensed signal representing the sensedload on the internal combustion engine, delivering the sensed signal ofthe load on the internal combustion engine to a controller operable toprovide output command signals of the load on the internal combustionengine, supplying air to the air intake passage of the internalcombustion engine with a supercharger comprising a positive airdisplacement device having at least one movable member operable to varythe effective air displacement of the positive air displacement devicesuch that it varies the trapped air volume generally at the point thatthe internal air compression of the supercharger begins, driving thesupercharger with the internal combustion engine to generate the airsupplied to the air intake passage of the internal combustion engine,varying the air supplied by the supercharger to the air intake passageof the internal combustion engine by operation of the movable memberresponsive to the command signals from the controller of the load on theinternal combustion engine to selectively boost the flow of airdelivered to the air intake passage of the internal combustion engine ator above the naturally aspirated flow of air to the air intake passageof the internal combustion engine, and introducing combustible fuel intothe piston chamber of the internal combustion engine responsive to thecommand signals from the controller corresponding to the boost of theflow of air delivered to the air intake passage of the internalcombustion engine to maintain a desired air to fuel ratio in the pistonchamber of the internal combustion engine.